"COM"，"USB"，“串行端口"之间有什么区别? [英] What's the difference between "COM", "USB", "Serial Port"?

问题描述

我对这三个概念感到困惑.

I am confused about the these 3 concepts.

我的理解是，Serial Port通常表示RS-232兼容端口(RS =推荐标准). USB代表Universal Serial Bus.因此，它的名称包含串行端口，它是否支持RS-232? Universal是什么意思?

My understanding is, Serial Port usually means RS-232 compatible port (RS = Recommended Standard). USB stands for Universal Serial Bus. So its name contains serial port, does it support RS-232? What does the Universal mean?

COM端口是什么意思?

And what does COM port mean?

对汉斯的回答有些理解:

Some understanding from Hans' answer:

为减少工作量，设备制造商通常会使其设备的行为也像串行端口设备一样.这取决于许多操作系统和语言库已经包含串行端口通信支持这一事实.尽管这种支持无法与真正的匹配设备驱动程序相提并论.

To reduce effort, device manufacturers usually make their device can behave like a serial port device as well. This relies on the the fact that many OS and language libraries have already included serial port communication support. Though such support is no comparable to a real matching device driver.

有关串行端口HOW-TO 的很好的参考文档.

A good reference doc about Serial Port HOW-TO.

顺便说一句， Linux文档项目真的很有用.

And btw, the Linux Document Project is really useful.

推荐答案

Serial port是一种使用UART芯片(通用异步接收器发送器)的设备.在过去，连接计算机的两种基本方法之一是并行端口，另一种是并行端口.串口很容易连接，不需要很多线.如果您想快速运行(并行速度通常是串行速度的8倍)，则并行很有用，但是电缆和连接器价格昂贵.并行I/O已从计算机设计中完全消失，而总线收发器的发展则赶上了这种并行收发器的发展，总线收发器是一种可以通过电线传输电信号的芯片.

Serial port is a type of device that uses an UART chip, a Universal Asynchronous Receiver Transmitter. One of the two basic ways to interface a computer in the olden days, parallel ports were the other way. Serial is simple to hook up, it doesn't need a lot of wires. Parallel was useful if you wanted to go fast, typ 8 times faster than serial, but cables and connectors were expensive. Parallel I/O has completely disappeared from computer designs, caught up by tremendous advances in bus transceivers, the kind of chip that can transmit an electrical signal down a wire.

COM来自MS-Dos，它是一个设备名称. 通信端口"的缩写. 1980年代的计算机通常在机器背面有两个串行端口，分别标记为COM1和COM2.该名称被保留到Windows中，大多数模拟串行端口的驱动程序都会创建一个名称为"COM"的设备. LPT是并行端口的设备名称，是"Line PrinTer"的缩写.

COM comes from MS-Dos, it is a device name. Short for "COMmunication port". Computers in the 1980's usually had two serial ports, labeled COM1 and COM2 on the back of the machine. This name was carried forward into Windows, most any driver that simulates a serial port will create a device with "COM" in its name. LPT was the device name for parallel ports, short for "Line PrinTer".

RS-232是用于串行端口的电信号传输标准.这是对设备要求极低的最简单的设备，仅支持点对点连接. RS-422和RS-485并不少见，每个信号使用双绞线，具有更高的抗噪能力，并允许多个设备相互连接.

RS-232 was an electrical signaling standard for serial ports. It is the simplest one with very low demands on the device, supporting just a point-to-point connection. RS-422 and RS-485 were not uncommon, using a twisted pair for each signal, providing much higher noise immunity and allowing multiple devices connected to each other.

USB表示通用串行总线.能够将微处理器集成到几毫米大小，几分钱的设备中.在1990年代后期，它取代了传统设备.它之所以具有通用性，是因为它可以支持许多不同类型的设备，从咖啡壶，磁盘驱动器到wifi适配器再到音频播放.它是串行的，只需要4根线.它是总线，您可以将USB设备插入任意端口.它与FireWire(一种非常相似的方法)竞争，并受到了Apple的拥护，但获得了滑坡的殊荣.

USB means Universal Serial Bus. Empowered by the ability to integrate a micro-processor into devices that's a few millimeters in size and costs a few dimes. It replaced legacy devices in the latter 1990s. It is Universal because it can support many different kinds of devices, from coffee-pot warmers to disk drives to wifi adapters to audio playback. It is Serial, it only requires 4 wires. And it is a Bus, you can plug a USB device into an arbitrary port. It competed with FireWire, a very similar approach and championed by Apple, but won by a land-slide.

这些天，串行端口仍在Windows上仍然有用的唯一原因是因为USB设备需要自定义设备驱动程序.设备制造商不像编写和支持驱动程序那样，通常会在其驱动程序中采用一种快捷方式，使其模仿旧版串行端口设备.因此，程序员可以对操作系统内置的串行端口以及任何语言运行时库使用旧版支持.顺便说一句，这些模拟器并不是完美的支持，它们从来都不能很好地支持即插即用.发现要打开的特定串行端口非常困难.而且，当程序使用USB设备时，这些驱动程序通常会误以为无法诊断.

The only reason that serial ports are still relevant in on Windows these days is because a USB device requires a custom device driver. Device manufacturers do not like writing and supporting drivers, they often take a shortcut in their driver that makes it emulate a legacy serial port device. So programmers can use the legacy support for serial ports built into the operating system and about any language runtime library. Rather imperfect support btw, these emulators never support plug-and-play well. Discovering the specific serial port to open is very difficult. And these drivers often misbehave in impossible to diagnose ways when you jerk a USB device while your program is using it.

这篇关于"COM"，"USB"，“串行端口"之间有什么区别?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！